Hard Drive Tray for Precision 3640 Desktop

Can anyone let me know the part number or where to purchase several of the plastic "trays" to install a 3.5 inch hard drive in a new Precision 3640 Desktop ?

Are these plastic "trays / bays / caddies" compatible with other Dell desktop lines?  which might yield more more options for purchasing.

I chatted with Dell support and they mentioned 575-BBWY but this part doesn't appear in any searches on the Dell site. Another Dell support chat mentioned that they were available only refurbished for $$ but wouldn't give a part number

The Service manual shows these as blue plastic pieces, but does not refer to a part number: